Download Relative abundance I: commonness and rarity

Relative abundance I:
commonness and rarity
Bio 415/615
Questions
1. How does a rank abundance distribution
quantify commonness and rarity?
2. What are the three components of the
rarity scheme of Rabinowitz?
3. What are three ecological processes
that lead to rarity?
4. Why might you manage rare species like
chestnut and Venus flytrap
differently?
Recall rank-abundance distributions (RADs)
% of individuals
889 oak trees, 100 bay trees, 10 maple trees, 1
birch tree
100
10
1
.1
.01
1
2
3
4
Rank by abundance
Length of the line
changes with diversity
Slope generally
changes with diversity
Slope changes because
of the change in
evenness that
generally correlates
with system diversity
What would the slope
be in a perfectly even
community?
What influences dominance or
non-equitability?
•
Conditions that promote competitive
suppression
–
•
Low disturbance, abundant resources
Conditions that deny species
membership due to harsh conditions
(‘stress’)
–
allow ‘specialists’ to dominate
Grime’s
‘hump-backed
model’ model
of local diversity
Species richness
4. Local heterogeneity
5. Species pool size (how many
potential colonists?)
1. Dominance (competition)
Standing biomass (sometimes productivity)
2. Stress = reduces potential production
J.P. Grime 1979
3. Disturbance = removes biomass
What influences dominance or
non-equitability?
RADs: Disturbance, succession
Bazzaz 1975
Heath
Fir
Sprucerhodo
Pine heath
Pine forest
Red oak
Geometric
(logseries)
Rich coves
Whittaker 1965
lognormal
Rich, mesic
Dry or cold
7 Forms of Rarity based on three characteristics: geographic range,
habitat specificity, and local population size (Rabinowitz 1981)
GEOGRAPHIC
RANGE
HABITAT
SPECIFICITY
LARGE
SMALL
WIDE
NARROW
WIDE
NARROW
Locally
abundant over
a large range
in several
habitats
Locally abundant
over a large
range in a
specific habitat
Locally abundant
in several
habitats but
restricted
geographically
Locally abundant
in a specific
habitat but
restricted
geographically
(Common)
(Predictable)
(Unlikely)
(Endemic)
Constantly
sparse over a
large range
and in several
habitats
Constantly sparse
in a specific
habitat but over
a large range
Constantly
sparse and
geographically
restricted in
several habitats
Constantly
sparse and
geographically
restricted in a
specific habitat
(Non-existent?)
(Endemic)
LOCAL POP.
SIZE
LARGE,
DOMINANT
SOMEWHERE
SMALL,
NONDOMINANT
(Sparse)
(Predictable)
7 Forms of Rarity based on three characteristics: geographic range, habitat
specificity, and local population size (Rabinowitz 1981)
GEOGRAPHIC
RANGE
HABITAT
SPECIFICITY
LARGE
SMALL
WIDE
NARROW
WIDE
NARROW
Locally
abundant over
a large range
in several
habitats
Locally abundant
over a large
range in a
specific habitat
Locally abundant
in several
habitats but
restricted
geographically
Locally abundant
in a specific
habitat but
restricted
geographically
(Common)
(Predictable)
(Unlikely)
(Endemic)
Constantly
sparse over a
large range
and in several
habitats
Constantly sparse
in a specific
habitat but over
a large range
Constantly
sparse and
geographically
restricted in
several habitats
Constantly
sparse and
geographically
restricted in a
specific habitat
(Non-existent?)
(Endemic)
LOCAL POP.
SIZE
LARGE,
DOMINANT
SOMEWHERE
SMALL,
NONDOMINANT
(Sparse)
(Predictable)
Rarity in the British Flora (Rabinowitz et al.); 39% no component of rarity
3 kinds of rarity; evidence they are independent
59% Narrow Habitat; 15% Small Range; 7% Small Population
GEOGRAPHIC
RANGE
HABITAT
SPECIFICITY
LOCAL POP.
SIZE
LARGE,
DOMINANT
SOMEWHERE
SMALL,
NONDOMINANT
LARGE
WIDE
NARROW
SMALL
WIDE
NARROW
Causes of Rarity—Natural
Ecological, innate:
• Innate biology, Narrow niche, rarity of
conditions, climate change
• High trophic level species
• Vulnerability to natural biological change
• Disease, herbivory, predation, mutualism
Historical:
• Poor dispersal relative to habitat
dispersion, historical limits, climate change
• Recently evolved
Causes of Rarity—Imposed
1. Vulnerability to loss of dynamic process: fire,
flood, beaver, disease, herbivory, predation
–
2.
3.
4.
5.
Increase of white-tailed deer, Loss of
panther, elk
Sensitive to chemical, physical changes
Found in human-exploited habitats
Exploited species
Area & isolation sensitive species
Pseudo-rarity
• Global scale is not the only scale at
which populations are managed:
–
–
–
–
Nations
States
Counties / Cities
Parks
• Why are species rare
at these smaller scales?
Geum triflorum, ‘prairie smoke’
Pseudo-rarity
• Global scale is not the only scale at
which populations are managed:
–
–
–
–
Nations
States
Counties / Cities
Parks
• Why are species rare
at these smaller scales?
Geum triflorum, ‘prairie smoke’
Pseudo-rarity
• Global scale is not the only scale at
which populations are managed:
–
–
–
–
Nations
States
Counties / Cities
Parks
• Why are species rare
at these smaller scales?
Geum triflorum, ‘prairie smoke’
Intrinsic Extinction Vulnerability
Local endemics: small range, habitat narrow, island
species
Small population size
Large area needs
Large body size-large home range-high trophic level
Species of productive habitats used by people
Migratory species
Highly concentrated populations for breeding
Limited dispersal ability
Low population growth rate
Low genetic variation
High dependence on species that are extinction
vulnerable
Types of rarity: American chestnut
• One of the most common, dominant
trees of the eastern US before disease
introduction
• NOW: still widespread but only in small
shrub form
Large range,
locally rare
Endothia parasitica -- Chestnut blight
A Chinese fungus
Chestnut
Range
collapse of
American
chestnut
after the
introduction
of chestnut
blight
Many species were associated with chestnut, so
many species participated in the “recovery”
Nonetheless:
Loss of consistent hard mast
Lower carrying capacity for wildlife
like black bears
7 species of butterflies extinct
Possibly other insects
(Butterflies are conspicuous and
better known that other groups)
Types of rarity: Venus Fly Trap, Dionaea muscipula
Endemic
(locally
abundant)
Oconee Bell -- Shortia galacifolia
Endemic
(locally
abundant)
"The fairest bloom the mountain knows
Is not an iris or a wild rose
But the little flower of which I'll tell
Known as the brave acony bell.”
From "Acony Bell", by Gillian Welch and David Rawlings
The story of Shortia
1788, December 9 & 11—Collected by Michaux
He called it “a new plant” in his journal from
“les hautes montaignes de Caroline”
1839—Unnamed & undescribed specimen discovered
by Asa Gray in the Paris Herbarium
Gray named it for Dr. Charles Short
Gray searched on 3 occasions
1877—Rediscovered on Catawba River near Marion, NC
by George M. Hyams (89 years since discovery!)
1886—C. S. Sargent found original local (Keowee River)
using Michaux journal
Shortia galacifolia
Types of rarity: Rugelia nudicaulis
Endemic
(locally
abundant)
Torreya taxifolia
Endemic
(rare)
Types of rarity: yellowwood
Sparse
Types of rarity: baldcypress
Predictable
(specialist)
Types of rarity: Fraser fir
Specialist
endemic